Part 5 - Radar Systems Flashcards
What does radar stand for?
Radio Detection and Ranging
What are the two basic classifications of radar?
Primary and secondary
An active radar does what?
It transmits a high powered RF pulse and receives a weaker return that has reflected off a target
Stimulate and response describes what type of radar?
Secondary radar
Pulse modulation is a process normally used on aircraft communication systems, true or false?
False, it’s used on radar
A transponder which is part of a secondary radar system will give a “reply” once it has been “interrogated” by a primary radar - true or false?
True
What frequencies are normally used for airborne radar?
1 GHz to 15 GHz
A radar transmits short bursts of EM energy to receive what information about a target?
Range, bearing and height
Inside the transmitter, what is the purpose of the modulator?
Functions as an electronic high power switch, triggered by pulses from the master timing unit
Will produce pulses of the correct pulse duration and frequency to switch the magnetron on and off
The master timing unit output pulse is what type of pulse?
A synchronisation pulse which recur at precise and regular time intervals
Determines the pulse recurrence frequency (PRF) of the equipment
If the Pulse Repetition Period (PRP) is 2000μs, and the pulse duration is 1μs, what will be the resting time?
1999μs
The number of radar pulses produced in 1 second is known as?
Pulse Repetition Frequency (PRF)
If a radar has a PRF of 500 Hz, what will the PRP be?
2 ms
The ratio of the pulse duration to the PRP is known as what?
The pulse duty factor or duty cycle
If the pulse duration is 1μs and the PRP is 3000μs, what is the pulse duty cycle?
1/3000
What is the formula to calculate the mean power (PA) of a radar pulse?
PMTDPRF
If a pulse has an average power = 240W, max power = 400 kW and PD = 1μs, what is the PRF?
Mean power/(maximum power*PRF)
Parabolic and flat plate are type of what?
Radar aerial
A TxRx switch does what?
Automatically connects the Tx to the aerial for the duration of each transmitted pulse, then switches so that the Rx is connected to the aerial during the interpulse period
Also known as a Duplexer
A Rx must be very … in order to detect the weak radar returns from distant targets?
Sensitive
How long will a radar pulse take to travel 1nm and back?
12.36μs
Calculate the distance of an object that provides a return pulse after 123.6μs?
10nm
On a partial PPI radar display, how is the bearing read?
From the dead ahead position, to left and right (port and stbd)
A radar pulse travels 100nm with a transmission power of 1MW. If the power is doubled, what will the range be?
Doubling the power, multiplies the range by 1.19, therefore 119nm